cylinder head question/predicament?

[Solidhank]

So I had a 350 rocket. After taking it apart due to overheating and scoring the cylinder wall I noticed that one head is a #7 and the other a #5. After looking into it i found that small block heads from that time were identical in many ways besides chamber sizes and after looking into chamber sizes theyre both listed to be 64cc's. So basically what I've gathered is that the only difference in these heads are the years they were manufactured. Am I missing something here that could have caused engine failure?

 

[truracer20]

#5 heads came on 68 and 69 engines and did not have hardened seats, #7 heads came on 71 & 72 engines and only 72's had hardened seats. Modellos tech reference book says the #5's had 68cc chambers while the #7's had 69cc chambers. Both heads had 1.875" intake and 1.562" exhaust valves EXCEPT 1968 #5 W-31 heads, they had 2.00" intake and 1.625" exhaust valves.
Look to see if any exhaust valves are sunk into the seats, that would be caused by using unleaded fuel with soft seats, and could be the cause of your issues.
Or the seats may have been replaced sometime during the past 46 years.

 

[DoubleV]

The only significant difference between the 5,6,7, and 7a heads are the valve rotators. I don't recall which years had them but I think the 5's didn't have any then in later years they added them on the exhaust side then later on both intake and exhaust.

The chamber sizes are all the same. 64cc's is the blueprint spec but you'll never find a set that small. They all usually measure out to about 68-70cc's.

Olds heads usually don't have any issues with sunken seats even without hardend exhaust seats because the quality of the Olds iron was good.